Android 仅当它在前台时才从 BroadcastReceiver 通知活动

Inform Activity from a BroadcastReceiver ONLY if it is in the foreground

提问by Zordid

Maybe it's easy, but I couldn't really figure this out right so far... I got a BroadcastReceiverwaiting to get triggered by the AlarmMangager - this works fine.

也许这很容易，但到目前为止我无法真正弄清楚这一点......我BroadcastReceiver等待被AlarmMangager触发 - 这很好用。

Now: because the event, if it occurs, needs to refresh some elements on screen of the main Activity, I would like to send an Intent from that background BroadcastReceiver to my Activity - but onlyif it is currently in the foreground, aka active.

现在：因为该事件（如果发生）需要刷新主 Activity 屏幕上的某些元素，我想从该后台 BroadcastReceiver 向我的 Activity 发送一个 Intent -但前提是它当前处于前台，即活动状态。

If it is not running or not visible, I don't care - and the last thing I want to do is start the Activity by my intent! I handle repainting of the views in my onResume() method, so I don't care at all.

如果它没有运行或不可见，我不在乎 - 我想做的最后一件事就是按照我的意图启动 Activity！我在 onResume() 方法中处理视图的重绘，所以我根本不在乎。

Any hints on how to do that? Thanks!

关于如何做到这一点的任何提示？谢谢！

EDIT:my BroadcastReceiver is waiting for alarms that must be notified to the user. So, it must be there and declared in the manifest. The problem is: it will have to decide whether the mentioned Activity is currently up in front or not.

编辑：我的 BroadcastReceiver 正在等待必须通知用户的警报。因此，它必须存在并在清单中声明。问题是：它必须决定所提到的 Activity 当前是否在前面。

回答by Binh Tran

I believe that you're familiar with AlarmManager now (creating a new Alarm, register a receiver...) so I will not talk about that. Just give you a solution for your question.

我相信你现在对 AlarmManager 很熟悉（创建一个新的警报，注册一个接收器......）所以我不会谈论那个。只是为你的问题提供一个解决方案。

Instead of registering a BroadcastReceiver in a class file and in manifest, you only create a new BroadcastReceiver in your activity, and then, register it in onResume method, and unregister it in onPause method, sth like this in your activity:

无需在类文件和清单中注册 BroadcastReceiver，您只需在您的活动中创建一个新的 BroadcastReceiver，然后在 onResume 方法中注册它，并在 onPause 方法中取消注册，在您的活动中像这样：

private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
      //do something       
    }
};

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mIntentFilter = new IntentFilter();
    mIntentFilter.addAction("your alarm action");
    ...
}

@Override
protected void onResume() {
registerReceiver(mIntentReceiver, mIntentFilter);
    ...
super.onResume();
}

@Override
protected void onPause() {
unregisterReceiver(mIntentReceiver);
    ...
super.onPause();
}

The receiver will only receive the alarm intent when your activity is in foreground :)

当您的活动处于前台时，接收器只会收到警报意图 :)

(Sorry if my English is not clear)

（对不起，如果我的英语不清楚）

回答by Chris Boyle

So this is almost Bino's answer, but: instead of moving the receiver into the activity, use two receivers, with different Intents. The first one is your original alarm Intent, with a receiver registered in the manifest as you already have, and then that receiver sends a second broadcast intent, which is handled by a receiver registered by the activity as Bino says.

所以这几乎是 Bino 的答案，但是：不要将接收器移动到活动中，而是使用两个具有不同意图的接收器。第一个是您的原始警报意图，在清单中注册了一个接收器，因为您已经拥有，然后该接收器发送第二个广播意图，由活动注册的接收器处理，如 Bino 所说。

I've done this in my own timer project, on github. Here are the alarm receiverand the requery receiver. Hope that helps.

我已经在我自己的计时器项目中完成了这个，在 github 上。这是警报接收器和重新查询接收器。希望有帮助。